Circuit Description - Kenwood kac-719 Service Manual

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Instruction manual (5 pages)

Instruction manual (5 pages)

Instruction manual (13 pages)

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KAC-719

SP P-CON Switching Circuit

When the SP output from the head unit is connected to SP IN, the power can

be switched ON/OFF based on the DC voltage of the SP output. However, As

certain head unit models output DC permanently or generate a click during

switching OFF, it is required to provide the capability of previous P-CON

switching. A circuit which can perform the switching without using a switch

is described below.

This circuit performs switching by inhibiting the operation of the S-P-CON

circuit when a voltage is applied to the P-CON pin.

Circuit operation description

When the head unit is connected to SP-INN, the DC component in the SP output

turns Q38 ON through D32 and R158.

When a voltage is applied to the P-CON pin under this condition, Q45 is

turned ON via R188, positive feedback is applied by combination of Q45 and

Q46, Q45 and Q46 are held at ON, so the voltage at point (A) is almost 0 V

and the SP-P-CON circuit is not activated.

This circuit holds the ON status while the DC voltage from SP is present.

Therefore, in this condition, the P-CON circuit continues functioning. To

cancel the functioning, the voltage at the SP-IN pin should go 0 V.

to P-CON terminal

from SP-P-CON

Connect a cassette receiver or other receiver.